I've seen plenty of postings that one should not vent bathroom fans to
soffit or ridge vents. I completely agree about not using the soffits.
But how about using some blue foam, or other material, and making
some sort of 4" round pipe to ridge vent adapter. Think of all the
sheet metal HVAC adapters at home centers. But I'm thinking of just
fabricating something that custom fits my roof/ridge vent at one end
and a 4" round opening at other end. I can purchase a 4" sheetmetal
colar to make the round opening in the foam. This would force 99% of
the moist bathroom air directly out a portion of the ridge. The foam
adapter would protect the roof sheathing from moisture, plus it's
easily built on site.

Downfalls? reduced ridge ventilation for the attic - but I doubt
enough to have any impact

Appreciate any comments...

Thanks!

-Mike